046
FXUS65 KBYZ 210705
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
105 AM MDT WED OCT 21 2026
KEY MESSAGES
- WARM AND DRY CONDITIONS THROUGH THURSDAY.
- STORM SYSTEM THURSDAY NIGHT THROUGH SATURDAY BRINGS LOWER
ELEVATION RAIN AND MOUNTAIN SNOW; GREATEST TOTALS FORECAST WEST
OF BILLINGS.
- WINDY CONDITIONS POSSIBLE WITH THE LATE WEEK WEATHER SYSTEM.
- MOSTLY DRY AND SEASONABLY COOL LATE WEEKEND THROUGH EARLY NEXT
WEEK.
DISCUSSION
NEXT 7 DAYS ...
THE NEXT COUPLE OF DAYS (TODAY AND THURSDAY) WILL FEATURE FAIRLY
BENIGN WEATHER. OUTSIDE OF A WIDELY ISOLATED SHOWER IN THE HIGH
TERRAIN, SUNNY SKIES AND ABOVE AVERAGE TEMPERATURES WILL PERSIST.
BE SURE TO GET OUT AND ENJOY IT IF YOU CAN AS BIG CHANGES ARE IN
STORE COME FRIDAY.
THROUGH THE DAY THURSDAY, THE CUTOFF LOW OFF THE COAST OF
CALIFORNIA WILL MOVE INLAND AND BEGIN TO MERGE WITH A DIGGING
TROUGH COMING OUT OF THE GULF OF ALASKA. THESE WILL TRANSITION
INTO A SPLIT-FLOW TROUGH AS THEY BEGIN TO IMPACT OUR AREA EARLY
FRIDAY MORNING. BOTH THE ECMWF AND GFS OPERATIONAL RUNS AT 00Z ARE
DEPICTING THE SOUTHERN ENERGY MOVING UP THROUGH UT AND SE ID. THIS
WOULD PUT THE WESTERN 2/3 OF THE CWA UNDER GOOD DIFFLUENCE ALOFT.
MODELS ARE STILL DIFFERING IN JUST HOW MUCH MOISTURE WILL FALL
ALTHOUGH ALL ARE IN GOOD AGREEMENT THAT THE BULK OF IT WILL FALL
NEAR AND WEST OF BILLINGS.
MODELS HAVE BEEN SLOWLY TRENDING UPWARDS IN PRECIPITATION TOTALS
FOR LOCATIONS IN AND NEAR THE MOUNTAINS OF SOUTH-CENTRAL MONTANA
OVER THE PAST FEW RUNS. THIS WILL NEED TO BE WATCHED OVER THE
NEXT COUPLE OF DAYS TO ENSURE THAT THIS TREND CONTINUES AS ANY
LITTLE SHIFT IN A PIECE OF THIS DISJOINTED TROUGH COULD MAKE A
BIG DIFFERENCE. WHAT WE CAN SAY WITH SOME CERTAINTY, IS THAT
THERE WILL BE A DOWNSLOPE EFFECT ON THE NE FACING ASPECTS OF THE
MOUNTAINS. THIS REGION WILL BE IMPACTED BY A BRIEF PERIOD OF
UPSLOPE ON THE BACKSIDE OF THE SYSTEM WHICH WILL HELP TO MITIGATE,
BUT NOT COMPLETELY ELIMINATE, THE RAIN SHADOW EFFECT. ALTHOUGH
SNOW LEVELS WIL BE DROPPING THROUGH THE EVENT, IT APPEARS UNLIKELY
THAT ANY SNOW ACCUMULATION WILL OCCUR BELOW 6KFT. AS OF RIGHT NOW
THERE DOES NOT SEEM TO BE A NEED FOR ANY PRODUCT ISSUANCE IN
TERMS OF PRECIPITATION, BUT IF THE MODEL TRENDS CONTINUE, THE
WESTERN ZONES OF THE CWA WILL NEED TO BE WATCHED CLOSELY.
THE OTHER BIG STORY WITH THIS SYSTEM WILL, IN TRUE MONTANA
FASHION, BE THE WINDS. ON SATURDAY, THE TROUGH DIGGING OUT OF BC
WILL BRING WITH IT SOME BREEZY WINDS ALOFT. THE CURRENT MODEL RUNS
KEEP THE STRONGEST 700MB WINDS (50+ KTS) ALONG THE MT/SK BORDER
AND OUT OF OUR AREA. WITH THE SLIGHT NORTHWARD TREND OF THE
SOUTHERN ENERGY THIS MAKES SENSE DYNAMICALLY. THIS DOES NOT MEAN
THAT THERE WILL BE NO WINDS, JUST NOTHING STRONG IN THIS
SCENARIO. JUST AHEAD OF THE TROUGH, FRIDAY MORNING, THERE IS A
NARROW WINDOW FOR A GOOD GAP WIND SETUP IN LIVINGSTON. AS THE
TROUGH QUICKLY APPROACHES, SURFACE PRESSURE FALLS OVER THE PLAINS
NEAR BILLINGS WILL ACCOMPANY PRESSURE INCREASES OVER THE HIGH
TERRAIN NEAR YNP. AS LONG AS A DECENT INVERSION CAN SETUP
OVERNIGHT BEFORE THE CLOUDS MOVE IN, THE PRE-DAWN HOURS COULD BE
BREEZY AS WINDS GAP OUT OF THE PARADISE VALLEY.
LOOKING AHEAD, SOME WEAK TRAILING ENERGY BEHIND THE MAIN TROUGH
COULD BRING SOME SCATTERED LIGHT RAIN/SNOW SHOWERS THROUGH
MONDAY. TEMPERATURES WILL BE CLOSER TO AVERAGE, IF NOT JUST BELOW,
GOING INTO NEXT WEEK. THERE IS ALSO A GOOD SIGNAL THAT THE UPPER
LEVEL PATTERN WILL REMAIN VERY ACTIVE. ANY SORT OF DETAIL AFTER
MONDAY IS A HUGE QUESTION THOUGH AS ALL MODELS ARE SHOWING WILDLY
DIFFERENT THINGS WITH SOME PRETTY LARGE FEATURES. WMR
AVIATION
VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD WITH PASSING MID
AND HIGH CLOUDS. THERE IS A LOW CHANCE (15%) OF A FEW SHOWERS OVER
THE WESTERN MOUNTAINS THIS AFTERNOON AND EVENING. STP
PRELIMINARY POINT TEMP/POPS
TDY THU FRI SAT SUN MON TUE
-------------------------------------------------------
BIL 068 045/075 049/067 037/051 031/051 030/048 030/057
0/U 00/B 08/T 90/U 01/U 11/B 11/B
LVM 072 042/074 044/057 027/048 025/050 025/050 028/057
0/U 00/B 2+/W 90/U 01/B 11/B 12/W
HDN 071 040/076 045/071 032/052 026/054 027/051 025/058
0/U 00/B 08/T 90/B 00/U 11/B 11/B
MLS 072 045/074 048/074 035/049 030/052 030/048 030/054
0/U 00/U 01/B 70/B 01/B 11/B 11/B
4BQ 074 050/077 054/079 037/049 031/053 032/049 031/057
0/U 00/B 00/N 50/B 01/U 11/B 11/B
BHK 070 042/080 048/083 032/049 024/051 025/047 025/055
0/U 00/U 00/N 31/N 01/U 11/B 11/B
SHR 074 042/077 045/073 030/050 025/054 027/052 025/059
0/U 00/B 04/W 82/W 00/U 11/B 11/B
BYZ WATCHES/WARNINGS/ADVISORIES
MT...NONE.
WY...NONE.
WEATHER.GOV/BILLINGS
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